The blonde-haired celebrity chef made the surprise discovery when his great-uncle died, and is now keen to explore his family history further.

“It turns out I’m sixth-generation Sudanese. We only found out about it when my grandfather’s brother died but, as it happens, there are quite a few Olivers who are a bit swarthy and have got curly hair, so I suppose that may explain it,” Oliver told the Radio Times.

“Have a look at the picture of me on the cover of The Naked Chef, and you can see what I’m talking about.

“To be honest, I don’t have many details about the Sudan side of things, but I’d really like to go on [BBC genealogy programme] Who Do You Think You Are? to find out.”

Oliver’s latest Channel 4 television show is Jamie’s American Road Trip, in which he attempts to improve dietary habits in the US.

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Travelling through the Deep South, he was shocked by the depth of racism he encountered. “For the first time in my life, I heard the N-word used seriously, and it came as a shock to the system. We were talking about Obama’s election, and the comment that came back was, ‘In England, they’ve got a Queen. Over here we got a... ‘“

Oliver also said that he was appalled by the US health care system after meeting a restaurant owner in Augusta, Georgia, who was struggling to cover the cost of medical treatment for her disabled daughter.

He said: “It makes you think, doesn’t it? I mean, America may be a superpower, but at least in this country we don’t have to make a choice between sacrificing our children’s health and putting food on the table.

“There’s a lot of wonderful things about the US, and you’ve got to take your hat off to their ‘Yes we can’ mentality but, at the end of the day, I think maybe we haven’t got it so bad here after all.”